U.S. Pat. No. 3,321,517 discloses the preparation of the lactone perfluoro(3,6-dimethyl-2-oxo-1,4-dioxane), its hydrolysis to perfluoro(2-methyl-5-oxo-3-oxahexanoic)acid hydrate and the reaction of the hydrate with concentrated sulfuric acid to produce perfluoro(2-methyl-5-oxo-3-oxahexanoic)acid. No esters are disclosed.
U.S. Pat. No. 3,847,978 includes within its disclosure acids and esters of the formula ##STR6## wherein R is H or alkyl, X is CF.sub.3 COCF.sub.2, ##STR7## RO.sub.2 CCF.sub.2 or ##STR8## and m is an integer within the range 1-50. A similar disclosure appears in the related German Offenlegungschrift 1,817,826.
Japanese Kokai J52/120,983 discloses fluorocarbon copolymers having side chains which contain the moiety ##STR9## wherein R.sub.f is perfluoroalkyl of 1-5 carbon atoms, Y is F or R.sub.f, n is 0-3 and M is H, NH.sub.4 or a metal cation; also disclosed are cation exchange membranes of the copolymers.
U.S. Pat. No. 4,131,740 discloses alpha carboxylate-.omega.-vinyl ethers of the formula ##STR10## wherein R is alkyl of 1-6 carbon atoms and n is 1-6 and their preparation by pyrolysis of the corresponding acyl fluorides in the presence of Na.sub.2 CO.sub.3 or Na.sub.3 PO.sub.4 ; copolymers of the vinyl ethers and perfluorinated vinyl monomers such as tetrafluoroethylene are also disclosed.
U.S. Pat. No. 3,310,606 discloses perfluorinated divinyl ethers of the formula CF.sub.2 .dbd.CFO(CF.sub.2).sub.n OCF.dbd.CF.sub.2, wherein n is 2-24, their preparation by pyrolysis of the corresponding diacyl fluorides, and copolymers thereof with perfluorinated vinyl monomers.
South African Pat. No. 77/7158 discloses polyfluoroallyloxy compounds of the formula CF.sub.2 .dbd.CFCF.sub.2 OCF.sub.2 D wherein D can be linear or branched perfluoroalkyl of 1-10 carbon atoms, interruptable no more frequently than every second carbon atom by 1-4 ether oxygen atoms and having 0-2 functional groups. Although such disclosure embrances compounds of the formula ##STR11## wherein X' is SO.sub.2 F, COF, CO.sub.2 H, Cl, OCF.sub.2 CF.dbd.CF.sub.2, OCF.sub.2 CO.sub.2 R or CO.sub.2 R wherein R is CH.sub.3 or C.sub.2 H.sub.5, and p is 0-2, no method of preparing such compounds is provided.
U.S. Pat. No. 3,274,239 discloses fluorocarbon ethers which include those of the formula ##STR12## wherein n is an integer within the range 0-20, their preparation by the fluoride ion-catalyzed reaction of hexafluoropropene oxide and a perfluoroketone, and their pyrolysis to vinyl ethers.